1. Field of the Invention
The present invention relates to apparatus which are used to provide custom lighting. The present invention also relates to provision of shadowless lighting on an object, and a method of providing such shadowless lighting. The present invention also relates to providing shadowless light to objects of unusual shape, or having any one of crevices or interior surfaces.
The present invention also relates to provision of custom lighting that intentionally casts shadows about protuberances or other features of an object via directional lighting. The present invention is particularly related, but not exclusively, to the electronics manufacturing industry where electronics components and devices, for example, must be examined in either shadowless light or light that intentionally casts shadows, for instance, for quality control or inspection purposes.
2. Discussion of the Background
In the field of electronics manufacturing, it is often necessary to inspect a component visually under shadowless lighting conditions, so that every aspect and part of the surface topography of the component may be inspected for any surface defects.
There are known apparatus which are used for providing shadowless lighting, an example of which is U.S. Pat. No. 5,580,163 (Johnson). In this and other earlier patents, the ability to adjust various light elements is provided in the form of a mechanical apparatus that guides the lighting elements along predefined paths with respect to an object to be lighted. While the lighting elements in the prior art are moveable, such movement is constrained by the predefined mechanical guides.
Thus, these earlier apparatus are capable of providing shadowless lighting, but only when the object to be illuminated is of appropriate size and shape to be placed within the focus of these lighting elements. Such lighting apparatus are not able to readily accommodate irregular-shaped objects, or objects that do not conform to a light-receiving area of the apparatus. For example, the apparatus in the Johnson patent has a light-receiving area that is defined by a circular arrangement of lighting elements. Hence, the Johnson apparatus would not be readily adapted to provide lighting for a very long article that has dimensions which exceed the limited dimensions of the light-receiving area.
Examples of irregular shaped objects are those objects that would not receive shadowless lighting, if the lighting elements merely surround the periphery of the object, perhaps because of irregular contours on the surface of the object. For example, the object in FIG. 2B is unlikely to receive shadowless lighting if the lighting elements merely surrounded the periphery of the object as a whole, without taking into account the cavity 50. Regular geometric objects would not have this problem, but manufactured products commonly have irregularly shaped portions, for example overhangs, projections, or cavities.
Another problem with lighting apparatus in which the lighting elements have a restricted range of movement, is that such apparatus cannot usually be used readily to light internal crevices or surfaces. For example, an inside of a cylinder would not be well lighted because of shadows cast by lighting not directed to a surface on the inside of the cylinder.
Another known method of providing shadowless lighting is to create the lighting source from a bundle of fiber optics. The individual fiber optics are tied or bundled together so as to surround the object. Where necessary, the bundle of fibers may be shaped by cutting the ends of the fibers. This method of creating shadowless lighting is flexible because the lighting apparatus is fashioned from individual fibers, which provides great flexibility in the variety of objects that can be lighted. However, since a bundle of fibers must be created specifically for each object to be lighted, this approach to providing shadowless lighting tends to be expensive.
Furthermore, a lighting device created by using fibers cannot be readily adapted for lighting further objects that are shaped differently to the object for which the bundle of fibers was prepared for initially. There is no flexibility in being able to re-use such apparatus, unless the further objects to be lighted are of similar size and shape to the original object. Finally, it is difficult to use optical fibers to create a lighting apparatus that can illuminate internal surfaces or crevices.